Fluorine-containing 2-nitroimidazole derivatives

ABSTRACT

A 2-nitroimidazole derivative of the formula: ##STR1## wherein R f  is a group of the following formula (II) or (III): 
     
         --CH.sub.2 CFXCH.sub.2 OR.sub.1                            (II) 
    
     wherein X is a hydrogen atom or a halogen atom; R 1  is a group of the formula: ##STR2## wherein R 2  is a hydrogen atom, a hydroxyl group, a C 1  -C 3  alkyl group, a C 2  -C 4  acyl group, benzylidene or acetonide; R 3  is a hydrogen atom or a C 1  -C 3  alkyl group; Z is a hydrogen atom, COOY, COOR 3 , CONHOY, CONR 4  R 5  (wherein R 4  and R 5  are hydroxyl group-containing C 1  -C 3  alkyl groups or hydrogen atoms; Y is a hydrogen atom or a monovalent metal atom), an amino group, a hydroxyl group or OR 3  ; l is an integer of 1 to 3; o is an integer of 0 to 3; p is an integer of 0 to 2; q is an integer of 0 to 3; m and n are integers of 0 to 4; and 1≦m+n≦4 or ##STR3## wherein R 3 , X and p are the same as defined above; Z&#39; is the same as Z or is OCOOCH 3  ; r is an integer of 1 to 3; s is 0 or 1; t is an integer of 0 to 4 provided that when p=0, s≠0 and at least one X is a fluorine atom; and a radiosensitizer comprising said nitroimidazole derivative.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel fluorine-containing2-nitroimidazole derivatives and a radiosensitizer comprising the same,which facilitates inactivation of intractable hypoxic cells in malignanttumors by irradiation.

2. Description of the Related Art

To suppress reproduction or growth of malignant tumor cells, radiationexposure and administration of anti-tumor compounds or immunitysubstances are known and actually employed independently or incombination with surgical therapy. Among them, the radiation exposurehas been employed for a long time.

A hypoxic cell sensitizer (or radiosensitizer) which is a drug forincreasing sensitivity of the hypoxic cells against the radiation hasbeen developed since it is promising means for increasing effects ofradiotherapy.

Hitherto, various hypoxic cell sensitizers have been developed (cf. "Ganto Kagakuryoho" (Cancers and chemotherapy), Vol. 8, No. 11, November1981, 1659).

1-(2-Nitro-1-imidazolyl)-3-methoxy-2-propanol (Misonidazole), which isone of typical hypoxic cell sensitizers, is about twice as effective aswhen no Misonidazole is used. However, it is hardly administered in aneffective amount since it has strong neurotoxicity. No sensitizingeffect was confirmed from the results obtained by administering it inhuman beings (cf. Reference 4 cited in the above "Gan to Kagakuryoho").

To increase sensitizing activity of the radiation and simultaneously todecrease the neurotoxicity, nitroimidazole derivatives have been studied(cf. Japanese Patent Kokai Publication No. 12763/1987). However, theconventional derivatives have insufficient radiosensitization

It has been found that the radiosensitizing function of the azolecompounds is attributed to their azole rings while the side chaincontributes to their solubility in oils and pharmacologicalcharacteristics (Int. J. Radiat. Biol., 35, 1979, 151).

Compounds having a fluorine atom at a specific position in a moleculehave been increasingly used as medicines because of mimic effects of thefluorine atom or modification of methabolic inhibition effect andsolubility in oils (cf. "Kagaku no Ryoiki" (Chemical Fields), 35, 441(1981)).

SUMMARY OF THE INVENTION

One object of the present invention is to provide a novelfluorine-containing nitroimidazole derivative having a fluorinatedsubstituent on its imidazole ring.

Another object of the present invention is to provide afluorine-containing radiosensitizer which increases sensitivity of thehypoxic cells against radiation but has improved pharmacologicalcharacteristics and low toxicity and neurotoxicity.

Accordingly, the present invention provides a 2-nitroimidazolederivative of the formula: ##STR4## wherein R_(f) is afluorine-containing organic group and a radiosensitizer comprising saidnitroimidazole derivative.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing the relationships between the time afteradministration of the compounds used in Example 3 and the concentrationof the administered compounds in plasm, brain and tumor.

DETAILED DESCRIPTION OF THE INVENTION

In the nitroimidazole derivative (I) of the present invention, R_(f) isa group of the formula (II) or (III):

    --CH.sub.2 CFXCH.sub.2 OR.sub.1                            (II)

wherein X is a hydrogen atom or a halogen atom; R₁ is a group of theformula: ##STR5## wherein R₂ is a hydrogen atom, a hydroxyl group, a C₁-C₃ alkyl group, a C₂ -C₄ acyl group, benzylidene or acetonide; R₃ is ahydrogen atom or a C₁ -C₃ alkyl group; Z is a hydrogen atom, COOY,COOR₃, CONHOY, CONR₄ R₅ (wherein R₄ and R₅ are hydroxyl group-containingC₁ -C₃ alkyl groups or hydrogen atoms; Y is a hydrogen atom or amonovalent metal atom), an amino group, a hydroxyl group or OR₃ ; l isan integer of 1 to 3; o is an integer of 0 to 3; p is an integer of 0 to2; q is an integer of 0 to 3; m and n are integers of 0 to 4; and1≦m+n≦4 or ##STR6## wherein R₃, X and p are the same as defined above;Z' is the same as Z or is OCOOCH₃ ; r is an integer of 1 to 3; s is 0 or1; t is an integer of 0 to 4 provided that when p =0, s≠0 and at leastone X is a fluorine atom.

Preferred examples of the group R_(f) are as follows: ##STR7##

The nitroimidazole derivative (I) of the present invention may beprepared as follows (hereinafter "NI" means the group of2-nitroimidazol-1-yl):

(1) An epoxy compound of the formula: ##STR8## is addition reacted with2-nitroimdazole to form NI--CH₂ --CH(OH)CH₂ OA (wherein A is R₁). Thereaction temperature is from 0° to 100° C., preferably from 50° to 70°C. Although no solvent is required, the reaction may be carried out in asolvent such as dioxane, tetrahydrofuran (THF) and the like. Then, thehydroxyl group in the compound obtained is fluorinated with a suitablefluorinating agent (e.g. diethylaminosulfatrifluoride (DAST)) to formthe present compound (I) in an ether form.

(2) A fluorine-containing α,β-unsaturated carbonyl compound is additionreacted with 2-nitroimidazole to form NI--CH₂ CHFCOOB (wherein B is anester-forming group such as methyl or ethyl group).

NI--CH₂ CF₂ COOB can be obtained by the reaction of afluorine-containing oxetane with 2-nitroimidazole in an alcohol solventsuch as methanol or ethanol.

(3) An ester NI--CH₂ CFXCOOB is hydrolyzed and then reduced to formNI--CH₂ CFXCH₂ OH. The obtained alcohol compound is reacted with analkyl halide AX to obtain NI--CH₂ CFXCH₂ OA.

The present compound (I) in an amide form can be prepared by reactingNI--CH₂ CFXCOOA with an amine to form NI--CH₂ CFXCONDE (wherein D and Eare amide-forming groups such as a hydrogen atom and an alkyl group).

The 2-nitroimidazole derivative (I) of the present invention is usefulas a radiosensitizer. Its dose depends on the kinds of tumor and/or thecompound (I). Generally, it is from 20 to 10,000 mg in case of oraladministration, from 0.5 to 10,000 mg in case of injection or 20 to10,000 mg in case of suppository. An optimum dose may be determined by amedical practitioner according to symptom based on a kind of radiation,a radiation dose, fractionation of irradiation and the like.

The 2-nitroimidazole compound (I) of the present invention may beadministered in any suitable form. The compound (I) may be compoundedwith any carrier which is conventionally used in this field, andformulated by a conventional method.

The present invention is further illustrated by the followingPreparation Examples for the 2-nitroimidazole derivatives (I) andExamples showing the radiosensitization effect of the derivatives (I).

PREPARATION EXAMPLE 1 ##STR9##

To a solution of 1,2-O-isopropylideneglycerol (6.0 g, 50 mmol) andepichlorohydrin (18.5 g, 0.2 mol) in dioxane (50 ml), potassiumcarbonate (2.8 g, 50 mmol) was added and stirred for 3 hours at 70° C.The reaction mixture was filtered and the filtrate was concentrated toobtain 3-O-(2,3-epoxypropyl)-1,2-O-isopropylideneglycerol (6.9 g).

A mixture of the product (4.7 g, 25.2 mmol) and 2-nitroimidazole (1.9 g,16.8 mmol) was dissolved in ethanol (50 ml). Potassium carbonate (230mg, 1.7 mmol) was added to the solution and reacted at 70° C. for onehour. After the reaction, the reaction mixture was filtered and thefiltrate was concentrated. The residue was taken up in ethyl acetate(100 ml) and washed with water and a saturated sodium chloride solution.The organic phase was dried over magnesium sulfate, concentrated andpurified by silica gel column chromatography to obtain1-(2'-hydroxy-4'-oxa-6',7'-isopropylidenedioxyheptyl)-2-nitroimidazole(3.6 g).

¹ H-NMR (CDCl₃):δ=1.38 (3H, s, --CH₃), 1.42 (3H, s, --CH₃), 3.58 (4H, m,H₃ ', H₅ '), 3.72 (1H, dd, J=7 Hz, 8 Hz, H7'a), 4.08 (1H, dd, J=6 Hz, 8Hz, H₇ 'b), 4.16-4.84 (5H, m, H₁ ', H₂ ', H₆ ', --OH'), 7.07 (1H, s,H₅), 7.28 (1H, s, H₄).

To1-(2'-hydroxy-4'-oxa-6',7'-isopropylidenedioxyheptyl)-2-nitroimidazole(3.0 g, 10.0 mmol), dioxane (30 ml) was added and then DAST (2.0 g, 12.4mmol) was dropwise added while cooling with ice and stirred overnight ata room temperature. The reaction mixture was concentrated andpartitioned between ethyl acetate and water. The organic phase waswashed with water and dried over magnesium sulfate, concentrated andpurified by silica gel column chromatography to obtain1-(2'-fluoro-4'-oxa-6',7'-isopropylidenedioxyheptyl)-2-nitroimidazole(3) (2.2 g).

¹ H-NMR (CDCl₃)δ=1.39 (3H, s, H₃), 1.42 (3H, s, CH₃), 3.50-4.80 (9H, m,H₁ ', H₃ ', H₅ ', H₆ ', H₇ '), 4.60-5.30 (1H, dm, H₂ '), 7.19 (1H, s,H₅), 7.23 (1H, s, H₄).

¹⁹ F-NMR (CDCl₃ ; standard: TFA): 113.3 .

PREPARATION EXAMPLE 2

    NI-CH.sub.2 CHFCH.sub.2 OCH.sub.2 CH(OH)CH.sub.2 OH        (1)

To 1-(2'-fluoro-4'-oxa-6',7'-isopropylidenedioxyheptyl)-2-nitroimidazole(2.0 g, 6.7 mmol), 1N-HCl (20 ml) and THF (20 ml) were added and stirredfor 3 hours at a room temperature. After the reaction, the reactionmixture was concentrated and purified by silica gel columnchromatography to obtain1-(2'-fluoro-4'-oxa-6',7'-dihydroxyheptyl)-2-nitroimidazole (1) (1.0 g).

¹ H-NMR (DMSO-d₆): δ=3.20-3.86 (8H, m, H₃ ', H₅ ', H₇ ', --OH, --OH),4.40-5.30 (4H, m, H₁ ', H₂ ', H₆ '), 7.32 (1H, s, H₅), 7.78 (1H, s, H₄).

¹⁹ F-NMR (DMSO-d₆) standard : TFA): 112.9.

PREPARATION EXAMPLE 3

    NI--CH.sub.2 CHFCH.sub.2 OCH.sub.2 CHO                     (15)

To 1-(2'-fluoro-4'-oxa-6',7'-dihydroxyheptyl)-2-nitroimidazole (2.0 g,7.6 mmol), ethanol (10 ml), water (10 ml) and sodium metaperiodate (1.8g, 8.4 mmol) were added and stirred for one hour at a room temperature.After the reaction, the reaction mixture was filtered and partitionedbetween ethyl acetate and water. The organic phase was dried andconcentrated to obtain1-(2'-fluoro-4'-oxa-5'-formylpentyl)-2-nitroimidazole (15) (1.2 g).

PREPARATION EXAMPLE 4

    NI--CH.sub.2 CHFCH.sub.2 OCH.sub.2 CH.sub.2 OH             (11)

To a solution of 1-(2'-fluoro-4'-oxa-5'-formylpentyl)-2-nitroimidazole(1.0 g, 4.3 mmol) in methanol (10 ml), sodium borohydride (250 mg, 6.6mmol) were added while cooling with ice and stirred for one hour. Afterthe reaction, the reaction mixture was acidified by adding 1NHCl.Methanol was distilled off from the mixture. The mixture was extractedwith ethyl acetate. The organic phase was washed with water, dried overmagnesium sulfate, concentrated and purified by silica gel columnchromatography to obtain1-(2'-fluoro-4'-oxa-6'-hydroxyhexcyl)-2-nitroimidazole (11) (420 mg).

¹ H-NMR (CDCl₃)δ=3.60-4.02 (7H, m, H₃ ', H₅ ', H₆ ', --OH), 4.50-5.02(2H, m, H₁ '), 5.08 (1H, dm, J=48 Hz, H₁ '), 7.18 (1H, s, H₅), 7.44 (1H,s, H₄).

¹⁹ F-NMR (CDCl₃ ; standard: TFA): 112.8.

PREPARATION EXAMPLE 5 ##STR10##

To a solution of 1,3-O-benzylideneglycerol (5.0 g, 27.8 mmol) andepichlorohydrin (5.1 g, 55.6 mmol) in dioxane (50 ml), potassiumhydroxide (2.3 g, 41.7 mmol) was added and stirred for 4 hours at 70° C.The reaction mixture was filtered and the filtrate was concentrated andpurified by silica gel column chromatography to obtain2-O-(2',3'-epoxypropyl)-1,3-O-benzylideneglycerol (4.2 g).

¹ H-NMR (CDCl₃):δ=2.68 (1H, dd, J=2 Hz, 6 Hz, H₃ 'a), 2,84 (1H, dd, J=3hz, 6 Hz, H₃ 'b), 3.14-3.34 (1H, m, H₂ '), 3.40-3.64 (2H, m, H₁ '),3.86-4.21 (4H, m, H₁, H₃), 4.24-4.50 (1H, m, H₂), 5.56 ##STR11##

A mixture of the product (3.0 g, 12.7 mmol) and 2 nitroimidazole (1.4 g,12.7 mmol) was dissolved in ethanol (100 ml). Potassium carbonate (180mg, 1.3 mmol) was added to the solution and stirred for two hours at 60°C. After the reaction, the reaction mixture was filtered and thefiltrate was concentrated. The residue was taken up in ethyl acetate(200 ml) and washed with water and a saturated sodium chloride solution.The organic phase was dried over magnesium sulfate, concentrated andpurified by silica gel column chromatography to obtain1-[3'-(1,3-O-benzylideneglyceroxy)-2'-hydroxypropyl]-2-nitroimidazole(2.10 g).

To the product (2.0 g, 5.7 mmol), dioxane (20 ml) was added and thenDAST (1.4 g, 8.6 mmol) was dropwise added while cooling with ice andstirred overnight at a room temperature. After the reaction, excess DASTwas decomposed by adding water (5 ml). The reaction mixture wasconcentrated and partitioned between ethyl acetate and water. Ethylacetate phase was dried over magnesium sulfate, concentrated andpurified by silica gel column chromatography to obtain1[-3'-(1,3-O-benzilideneglyceroxy)-2'-fluoropropyl]-2-nitroimidazole (9)(1.3 g).

¹ H-NMR (DMSO-d₆): δ=3.30_(]4).42 (7H, m, H₃ ', H₅ ', H₆ ', H₁ "),4.64-5.14 (2H, m, H₁ '), 5.26 (1H, dm, J=46 Hz, H₂ '), 7.18-7.60##STR12##

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 112.6.

PREPARATION EXAMPLE 6

    NI--CH.sub.2 CHFCH.sub.2 OCH(CH.sub.2 OH).sub.2            (7)

To 1-[3'-(1,3-O-benzylideneglyceroxy)-2'-fluoropropyl]-2-nitroimidazole(1.0 g, 2.8 mmol), 1N-HCl (10 ml) and THF (10 ml) were added and stirredfor 3 hours at a room temperature. After the reaction, the reactionmixture was concentrated and purified by silica gel columnchromatography to obtain1-[3'-(1,3-dihydroglyceroxy)-2'-fluoropropyl]-2-nitroimidazole (7) (250mg).

¹ H-NMR (DMSO-d₆): δ=3.32-4.24 (7H, m, H₃ ', H₅ ', H₆ ', H₁ "),4.68-5.16 (4H, m, H₁ ', --OH, --OH), 5.22 (dm, 1H, J=46 Hz), 7.20 (1H,s, H₅), 7.46 (1H, s, H₄).

¹⁹ F-NMR (DMSO-d₆ ; standard TFA) 112.2.

PREPARATION EXAMPLE 7

    NI--CH.sub.2 CF.sub.2 CONH.sub.2                           (28)

To methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate (5.00 g, 21.3mmol), 10% ammonia solution (80 ml) in methanol was added and stirredfor 3 hours at a room temperature. Then, the reaction mixture wasconcentrated. Methanol (100 ml) was added to the concentrate andthroughly stirred. Insoluble fraction was filtered off. The filtrate wasconcentrated, subjected to silica gel column chromatography andrecrystallized from ethanol to obtain3-(2'-nitroimidazolyl)-2,2-difluoropropionic acid amide (2.57 mg). m.p.149.5°-151.5° C.

¹ H-NMR (DMSO-d₆): δ=5.40 (2H, t, H₃, J_(H).sbsb.3_(--F) =15 Hz), 7.41(1H, d, H₄ ', J_(H).sbsb.4_('--H).sbsb.5_(') =1 Hz), 7.82 (1H, d, H₅ ',J_(H).sbsb.5_('--H).sbsb.4_(')), 8.36 (1H, bs, --NH₂), 8.56 (1H, bs,--NH₂)

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 30.9

PREPARATION EXAMPLE 8

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CH.sub.2 CONH.sub.2     (22)

To a heterogeneous system of methyl3-(2'-nitroimidazolyl)-2,2-difluoropronionate (5.00 g, 21.3 mmol) andβ-alanine methyl ester hydrochloride (5.10 g, 36.5 mmol) in methanol (50ml), potassium hydroxide powder (4.6 g, 82 mmol) was gradually addedwhile stirring. Then, the reaction mixture was further stirred for onehour at a room temperature. The reaction solution was filtered withusing a Kiriyama funnel and the filtrate was concentrated andpartitioned between chloroform and water. The organic phase was driedover magnesium sulfate, filtered and concentrated. Ten % ammoniamethanol solution (40 ml) was added to the residue, stirred for two daysat a room temperature and then concentrated. The concentrate wassubjected to silica gel column chromatography and recrystallized from amixed solvent of chloroform/methanol to obtain3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropionylamino]propionic acidamide (3.50 g). m.p. 158.0°-160.0° C.

¹ H-NMR (DMSO--d₆): δ=2.42 (2H, t, --CH₂ CO, J=1 Hz), 3.31-3.60 (2H, m,--NHCH₂ --), 5.39 (2H, t, --CH₂ CF₂ --, J =15 Hz), 7.02 (1H, bs,--CONH₂), 7.40 (1H, d, H₅ ", J_(H).sbsb.5_("--H).sbsb.4_(") =1 Hz), 7.52(1H, bs, --CONH₂), 7.80 (1H, d, H₄ ", J_(H).sbsb.4_("--H).sbsb.5₄₁ =1Hz), 9.16 (1H, t, --CONH--, J=6 Hz).

¹⁹ F--NMR (DMSO-d₆ ; standard: TFA): 31.2.

PREPARATION EXAMPLE 9

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CF.sub.2 CONH.sub.2     (24)

To a solution of methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate(10.0 g, 42.5 mmol) in methanol (60 ml), 2,2-difluoro-3-amino-propionicacid amide (10.4 g, 83.8 mmol) was added and reacted for 20 hours at aroom temperature while stirring. Then, insoluble fraction was filteredoff from the reaction mixture. The filtrate was concentrated, subjectedto silica gel column chromatography and recrystallized from ethanol toobtain3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropionylamino]-2,2-difluoropropionicacid amide (4.98 g). m.p. 134.5°-135.5° C.

¹ H-NMR (DMSO-d₆): δ=3.95 (2H, dt, H₃, J_(H).sbsb.3_('--F) =15 Hz), 7.44(1H, s, H₄ "), 7.83 (1H, s, H₅ "), 8.20 (1H, bs, --NH₂), 8.42 (1H, bs,NH₂), 9.63 (1H, bt, --CONH--, J_(NH--H).sbsb.3 =6 Hz).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 30.9, 31.6.

PREPARATION EXAMPLE 10

    NI--CH.sub.2 CF.sub.2 CH.sub.2 OCH.sub.2 CONHCH.sub.2 CH.sub.2 OH (43)

To a suspension of sodium hydride (500 mg, 20.8 mmol) in dry THF (20 ml)which was cooled at -50° C., a solution of3-(2'-nitroimidazolyl)-2,2-difluoropropanol (2.0 g, 9.6 mmol) in dry THF(10 ml) and then a solution of ethyl bromoacetate (2.4 g, 14.4 mmol) indry THF were dropwise added. Then, the reaction mixture was graduallywarmed to a room temperature and stirred for 4 hours at the temperature.After the reaction, the mixture was cooled by ice. Ethanol (2 ml) wasadded to the mixture, concentrated and partitioned between ethyl acetateand water. The organic phase was dried over magnesium sulfate, filtered,concentrated and purified by silica gel column chromatography to obtainethyl 2-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]acetate (2.4 g)

The product (1.0 g, 3.4 mmol) was dissolved in dioxane (10 ml). To thesolution, ethanolamine (600 mg, 9.8 mmol) was added and heated for 9hours under reflux with stirring. The reaction solution was concentratedand partitioned between ethyl acetate and water. The organic phase wasdried over magnesium sulfate, filtered, concentrated and subjected tosilica gel column chromatography to obtain2[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]acetic acidhydroxyethylamide (280 mg).

¹ H-NMR (DMSO-d₆): δ=3.20-3.80 (5H, m), 4.08 (2H, t, --CF₂ CH₂ --, J=14Hz), 4.17 (2H, s, --CH₂ CO), 5.32 (2H, t, --CH₂ CF₂, J=15 Hz), 7.40 (1H,d, H₅ "), 7.83 (1H, d, H₄ "), 7.90 (1H, bt, NH).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 30.9.

PREPARATION EXAMPLE 11

    NI--CH.sub.2 CF.sub.2 CH.sub.2 OCH.sub.2 CONHOH            (44)

To sodium methoxide (28% solution in methanol; 3.9 g), methanol (10 ml)and then hydroxylamine hydrochloride (2.0 g, 28.8 mmol) were added andstirred for 2 hours at a room temperature. Then, the reaction mixturewas filtered. To the filtrate, ethyl2-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]acetate (600 mg, 2.0mmol) was added and heated for 12 hours under reflux with stirring. Thereaction solution was concentrated and partitioned between ethyl acetateand water. The organic phase was dried over magnesium sulfate, filtered,concentrated and purified by silica gel column chromatography to obtain2-[3'-(2"nitroimidazolyl-2',2'-difluoropropoxylacetic acid hydroxyamide(200 mg). m.p. 67°-68° C.

¹ H-NMR (DMSO-d₆): δ=4.08 (2H, t, --CF₂ CH₂ --, J=14 Hz), 4.17 (2H, s,CH₂ CO), 5.34 (2H, t, --CH₂ CF₂ --, J=15 Hz), 7.44 (1H, d, H₅ "), 7.84(1H, d, H₄ "), 9.14 (1H, bs, NH).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.3.

PREPARATION EXAMPLE 12

    NI-CH.sub.2 CF.sub.2 CH.sub.2 OCH.sub.2 CF.sub.2 CONHCH.sub.2 CH.sub.2 OH (45)

To a solution of methyl3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]-2,2-difluoropropionate(1.0 g, 3.0 mmol) in dioxane (10 ml), ethanolamine (370 mg, 6.0 mmol)was added and reacted for 5 hours at a room temperature with stirring.The reaction solution was concentrated and partitioned between ethylacetate and water. The ethyl acetate phase was dried over magnesiumsulfate, filtered, concentrated and purified by silica gel columnchromatography to obtain3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]-2,2-difluoropropionicacid hydroxyethylamide (550 mg). m.p. 67°-68° C. ¹ H-NMR (DMSO-d6):δ=3.24-3.76 (5H, m), 4.14 (2H, t, --CF₂ CH₂ --, J=13 Hz), 4.22 (2H, t,--OCH₂, J=14 Hz), 4.88 (1H, brt, --OH), 5.24 (2H, t, CH₂ CF₂, J= 15 Hz),7.42 (1H, d, H₅ "), 7.98 (1H, d, H₄ "), 8.93 (1H, brt, NH)

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.6, 34.6.

PREPARATION EXAMPLE 13

    NI--CH.sub.2 CF.sub.2 CH.sub.2 OCH.sub.2 CF.sub.2 CONH.sub.2 (46)

To a suspension of sodium hydride (700 mg, 29.2 mmol) in dry THF (50 ml)which was cooled to -30° C., a solution of3-(2'-nitroimidazolyl)-2,2-difluoropropanol (5.0 g, 24.0 mmol) in dryTHF (10 ml) and then a solution of tetrafluorooxatane (15.6 g, 120 mmol)in dry THF were dropwise added. Then, the reaction mixture was graduallywarmed to a room temperature and stirred for 3 hours at the temperature.After the reaction, the reaction mixture was cooled by ice. To themixture, methanol (5 ml) was slowly added. The reaction solution wasconcentrated and partitioned between ethyl acetate and water. Theorganic phase was dried over magnesium sulfate, filtered, concentratedand purified by silica gel column chromatography to obtain methyl3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]-2,2-difluoropropionate(2.2 g).

To the product (1.0 g, 3.0 mmol), 15 % ammonia methanol solution (50 ml)was added and stirred for 10 hours at a room temperature. The reactionsolution was concentrated and purified by silica gel columnchromatography to obtain3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropoxy]2,2-difluoropropionylamide(400 mg). m.p. 86°-87° C.

¹ H-NMR (DMSO-d₆): δ=4.20 (2H, t, CF₂ CH₂, J=13 Hz), 4.24 (2H, t,--OCH₂, J=14 Hz), 5.28 (2H, t, --CH₂ CF₂, J =15 Hz), 7.45 (1H, d, H₅ "),7.84 (1H, d, H₄ "), 8.24 (1H, bs, NH₂), 8.44 (1H, bs, NH₂).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.5, 34.4.

PREPARATION EXAMPLE 14

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CH.sub.2 CONHCH.sub.2 CH.sub.2 OH (47)

To a solution of methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate(10.0 g, 42.4 mmol) in methanol (50 ml), β-alanine methyl ester (8.38 g,81.3 mmol) was added and stirred for one hour at a room temperature.Then, the reaction solution was concentrated and partitioned betweenethyl acetate and a saturated sodium chloride solution. The organicphase was dried over magnesium sulfate, filtrated and concentrated.

To the residue, dioxane (25 ml) and then ethanolamine (3.5 ml, 58.0mmol) were added and heated for 4 hours under reflux. After thereaction, the solution was concentrated and partitioned between ethylacetate and a saturated sodium chloride solution. The organic phase wasdried over magnesium sulfate and filtered. The filtrate was concentratedand purified by silica gel column chromatography to obtain3-[3'-(2"-nitroimidazolyl)-2',2'-difluoropropionamido]propionic acidhydroxyethylamide (1.2 g).

¹ H-NMR (DMSO-d₆): δ=2.44 (2H, t, --CH₂ CO), 3.12-3.64 (6H, s), 4.79(1H, t, --OH, J=5.7 Hz), 5.38 (1H, t, H₃ ', J=14.8 Hz), 7.40 (1H, d, H₅"), 7.80 (1H, d, H₄ "), 8.05 (1H, brt, --CH₂ CONH, J=5.8 Hz), 9.16 (1H,brt, --CF₂ CONH, J=5.8 Hz).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.2.

PREPARATION EXAMPLE 15

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CONH.sub.2              (48)

To a solution of methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate(10.0 g, 42.4 mmol) in methanol (30 ml), a solution of glycineamide (5.0g, 67.6 mmol) in methanol was dropwise added and stirred for 30 minutesat a room temperature. Then, the insoluble fraction was collected byfiltration and recrystallized from methanol to obtain2-[3'(-(2"-nitroimidazolyl)-2',2'-difluoropropionamido]ethylamide (4.42g). m.p. 183.5°-185.0° C.

¹ H-NMR (DMSO-d₆): δ=3.79 (2H, d, --CH₂ CO--, J_(H).sbsb.2_(--NH) =6.0Hz), 5.35 (2H, t, --CH₂ CF₂ --, J_(H).sbsb.3_('--F) =15.0 Hz), 7.21 (¹H, bs, --NH₂), 7.34 (1H, d, H₅ "), 7.53 (1H, bs, --NH₂), 7.78 (1H, d, H₄"), 9.21 (1H, brt, --NH--, J_(NH--H).sbsb.2 =6.0 Hz).

¹⁹ F-NMR (DMSO-d₆ ; standard TFA): 31.4.

PREPARATION EXAMPLE 16

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CH.sub.2 CH.sub.2 OH    (49)

To a solution of methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate(2.0 g, 8.5 mmol) in dioxane (10 ml), n-propanolamine (1.0 g, 13.3 mmol)was added and stirred for 2 hours at 70 ° C. Then, the reaction solutionwas concentrated and partitioned between ethyl acetate and water. Theorganic phase was dried over magnesium sulfate, filtered, concentratedand subjected to silica gel column chromatography toobtain.3-(2'-nitroimidazolyl)-2,2-difluoropropionic acidhydroxypropylamide (1.7 g).

¹ H-NMR (DMSO-d₆): δ=1.76 (2H, quint, J=6 Hz, CH₂), 3.34 (2H, m, --CH₂OH), 3.46-3.76 (2H, m, NHCH₂), 4.68 (1H, t, --OH), 7.46, 7.86 (each 1H,d, H₅ ', H₄ '), 9.18 (1H, brt, NH).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.1.

PREPARATION EXAMPLE 17

    NI--CH.sub.2 CF.sub.2 CONH(CH.sub.2).sub.4 OH              (50)

To a solution of methyl 3-(2'-nitroimidazolyl)-2,2-difluoropropionate(1.0 g, 4.2 mmol) in DMF (10 ml), n-butanolamine (500 mg, 5.6 mmol) wasadded and stirred for 6 hours at a room temperature. Then, the reactionsolution was concentrated and purified by silica gel columnchromatography to obtain 3-(2'-nitroimidazolyl)-2,2-difluoropropionicacid hydroxybutylamide (450 mg).

¹ H-NMR (DMSO-d₆): δ=1.40-1.80 (4H, m), 3.16-3.44 (2H, m), 3.48-3.70(2H, m), 4.62 (1H, t, --OH), 5.42 (2H, t, CH₂ CF₂, J=14 Hz), 7.42 (1H,d, H₅ '), 7.82 (1H, d, H₄ '), 9.18 (1H, bt, NH).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.0.

PREPARATION EXAMPLE 18

    NI--CH.sub.2 CF.sub.2 CONHCH.sub.2 CH.sub.2 OCOOCH.sub.3   (51)

3-(2'-Nitroimidazolyl)-2,2-difluoropropionic acid hydroxyethylamide (6.0g, 22.7 mmol) was dissolved in a solvent mixture of methyl chloroformate(30 ml) and chloroform (30 ml) and cooled by ice. To the solution, asolution of pyridine (6.0 ml) in chloroform (30 ml) was dropwise addedover 2 hours. The completion of the reaction was confirmed by thin-layerchromatography. Then, the reaction solution was washed with dilutehydrochloric acid and water, dried over magnesium sulfate, concentratedand subjected to silica gel column chromatography to obtain methyl3-(2'-nitroimidazolyl)-2,2-difluoropropionamidoethoxyformate (6.89 g).m.p. 50.5°-52.5° C.

¹ H-NMR (DMSO-d₆): δ=3.56 (2H, dt, J=5.7 Hz, NHCH₂), 3.86 (3H, s,--CH₃), 4.50 (2H, t, J=5.7 Hz, --CH2CO--), 5.38 (2H, t, J=14.8 Hz, --CH₂CF₂ --), 7.40 (1H, d, H₅ '), 7.78 (1H, d, H₄ '), 9.42 (1H, bt,--CONH--).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 31.1.

PREPARATION EXAMPLE 19

    NI--CH.sub.2 CONHCH.sub.2 CF.sub.2 CONH.sub.2              (52)

A solution of ethyl 2-(2'-nitroimidazolyl)acetate (2.0 g, 10.1 mmol) anddifluoro-β-alanineamide (2.5 g, 20.2 mmol) in methanol (10 ml) washeated for 10 hours under reflux. Then, the reaction solution wasconcentrated and partitioned between ethyl acetate and water. Theaqueous phase was concentrated and subjected to silica gel columnchromatography to obtain3-[2'-(2"-nitroimidazolyl)acetoamido]-2,2-difluoropropionic acid amide(200 mg).

¹ H-NMR (DMSO-d₆): δ=3.20 (2H, t, J=16 Hz, --CH₂ CF₂ --), 5.24 (2H, s,CH₂ CO), 7.38 (1H, d, H₅ "), 7.80 (1H, d, H₄ "), 7.44-8.50 (3H, m, NH,NH₂).

¹⁹ F-NMR (DMSO-d₆ ; standard: TFA): 33.4.

EXAMPLE 1

Radiosensitization effect on cells (ER in vitro)

To examine the in vitro radiosensitization effect of the present2-nitroimidazole derivative (I), 100,000 cells of Chinese hamster V-79cells were cultured in monolayer in a culture dish, and the V-79 cellsin a log phase were prepared.

A solution of a predetermined concentration (1.0 mM) of a compound to beexamined in a medium was added to the dish. After standing for 60minutes at 37° C., the dish was placed in a closed vessel at roomtemperature. Then, the vessel was purged with nitrogen for 10 minutes toexclude oxygen and X-ray was irradiated at a dose rate of 1.6 Gy/min.

After the irradiation, the cells were washed with phosphate buffer anddigested with trypsin into single cells. Then, a predetermined amount ofthe cells was introduced into 5 ml of a culture medium in a culture dishand cultured for 7 days at 37° C. After staining and washing with water,the number of colonies formed was counted.

The results are shown in following Table 1 as ER in vitro.

For comparison, the irradiation was carried out in the nitrogenatmosphere or in the air after adding the medium without the testcompound.

EXAMPLE 2

Radiosensitization effect on tumor transplanted in animal (ER in vivo)

To both thighs of male Bal/c mouse (8 weeks; 4 mice in a group), 10⁵ ofEMT-6 tumor cells were subcutaneously inoculated. After the diameter ofthe tumor reached about 1 cm, a solution of a compound to be examined insaline in an amount of 100 mg of the compound per kg wasintraperitonealy administered. After 40 minutes, X-ray was irradiated at450 rad/min. for 5 minutes and then the mouse was sacrificed.

After the whol body of the mouse was sterilized with 70% ethanol, thetumor was taken out. The tissue was homogenized and then digested bystirring for 50 minutes at 37° C. with adding 22 ml of trypsin. Thenumber of cells in the supernatant was counted. A predetermined amountof the cells was introduced in a plastic plate having a diameter ofabout 5 cm. To the plate, 5 ml of medium was added and cultured in a CO₂incubator. The plate containing the irradiated cells was removed fromthe incubator after 9 days, while a comparison dish containingunirradiated cells was incubated for 10 days. The cells were fixed bymethanol and strained by Giemsa stain. Then, the number of coloniesformed were counted.

The survival rate was calculated with using the data of the unirradiatedcells as control. The results are shown as ER in vivo in following Table1.

                  TABLE 1                                                         ______________________________________                                        Rf        ER in vitro                                                                              ER in vivo                                                                              LD.sub.50 (mg/kg)*.sup.2                       ______________________________________                                        (1)       1.49       1.38      2700                                           (11)      1.66       1.52      --                                             (22)      1.46       1.58      2800                                           (24)      1.76       1.41      2600                                           (28)      1.48       1.32      1100                                           (43)      1.54       1.38      >2000                                          (44)      1.68       1.48                                                     (45)      1.63       1.40      >1600                                          (46)      1.58       1.45                                                     (47)      1.43       1.38      >2000                                          (48)      1.61       1.49      2200                                           (51)                           >3000                                          Comparative                                                                             1.50       1.43      1200                                           (1)*.sup.1                                                                    ______________________________________                                         Note:                                                                         *.sup.1 Misonidazole [Rf = --CH.sub.2 CH(OH)--CH.sub.2 OCH.sub.3 ] was        used for comparison.                                                          *.sup.2 For determination of LD.sub.50, female ICR mice of 5 weeks were       used.                                                                    

EXAMPLE 3

Distribution of the radiosensitizer in a mouse body

To a right thigh of each of eight female C3H mice (8 weeks), SCO VIItumor cells were subcutaneously inoculated. After about two weeks atwhich the tumor reached 10 mm, a solution of a compound to be examinedin saline at a predetermined concentration was intravenouslyadministered (for example, 200 mg of the compound per kg). After 5, 10,15, 20, 30, 40, 60 and 90 minutes from the administration, an amount ofblood was sampled from the eye socket and then the mice were sacrificed.The tumor and the brain were taken out and weighed. They werehomogenized in 10 time volume of pure water. Then, to the homogenate,methanol of two time volume of the homogenate was added and thoroughlystirred followed by centrifugation. The supernatant was analyzed withliquid chromatography to find the distribution of the compound in eachorgan. The results for the compound (22) and the comparative compound(1) are shown in FIG. 1.

It has been shown that the present compounds have less tendency to passthe blood-brain barrier and therefore is less neurotoxic than thecompounds disclosed in Japanese Patent Kokai Publication No. 20456/1988.

What is claimed is:
 1. A 2-nitroimidazol derivative of the formula:##STR13## wherein R_(f) is a group of the following formula (II) or(III):

    --CH.sub.2 CFXCH.sub.2 OR.sub.1                            (II)

wherein X is a hydrogen atom or a halogen atom; R₁ is a group of theformula: ##STR14## wherein R₂ is a hydrogen atom, a hydroxyl group, a C₁-C₃ alkyl group, a C₂ -C₄ acyl group, benzylidene or acetonide; R₃ is ahydrogen atom or a C₁ -C₃ alkyl group; Z is a hydrogen atom, COOY,COOR₃, CONHOY, CONR₄ R₅ (wherein R₄ and R₅ are hydroxyl group-containingC₁ -C₃ alkyl groups or hydrogen atoms; Y is a hydrogen atom or amonovalent metal atom), an amino group, a hydroxyl group or OR₃ ; is aninteger of 1 to 3; o is an integer of 0 to 3; p is an integer of 0 to 2;q is an integer of 0 to 3; m and n are integers of 0 to 4; and 1≦m+n≦4or ##STR15## wherein R₃, X and p are the same as defined above; Z' isthe same as Z or is OCOOCH₃ ; r is an integer of 1 to 3; s is 0 or 1; tis an integer of 0 to 4 provided that when p=0, s≠0 and at least one Xis a fluorine atom.